The organic electroluminescent device (OLED), in comparison with other flat panel display technology, has such advantages as self luminescence, high luminance, wide visual angle, high resolution, low energy consumption, lightness and thinness and the like, thus being widely used.
A traditional organic electroluminescent element is of a multi-layered structure, its principle being that an organic electroluminescent material layer is provided between the anode layer and the cathode layer to produce electroluminescence. The organic electroluminescent element can be divided into two classes according to the material used thereby: one is the light-emitting diode of small molecules mainly using dye and pigment material, known as OLED (Organic Light-Emitting Diode) or OEL (Organic Electroluminescence), and the other is the light-emitting diode mainly using polymer material, known as PLED (Polymer Light-Emitting Diode) or LEP (Light-Emitting Polymer). According to the color of the light emitted by an organic electroluminescent element, the material of the organic electroluminescent material layer mainly consists of three kinds of electroluminescent material which are in red (R), in blue (G) and in blue (B). For the purpose of full-color display, each pixel unit in an organic electroluminescent display panel includes three sub-pixel units R, G, and B, and the organic electroluminescent element emitting light in one color corresponds to one sub-pixel unit.
There are mainly two kinds of thin film deposition method for the organic electroluminescent display device: vacuum evaporation and solution process. The vacuum evaporation is suitable for organic small molecule material, good in film-forming uniformity, comparatively mature in technology, but large in equipment investment, low in material utilization ratio, low in Mask alignment accuracy for large size products. The solution process includes spin coating, ink jet printing, nozzle painting and the like, suitable for polymer material and soluble small molecule material, and characterized by being low in equipment cost, highly advantageous in large scale production and large size product.
For evaporation process, although medium and small size organic electroluminescent display devices have been mass-produced, resolution thereof is still much lower than that of LCDs, whereas it is difficult to mass-produce the large size organic electroluminescent display devices due to low Mask alignment accuracy in the process of manufacturing the sub-pixel units; for solution process, although the large and small size prototypes of organic electroluminescent display devices constantly appear, they have not been mass-produced yet, and resolution thereof is not high due to the accuracy of film-forming equipment.
Therefore, how to manufacture OLED devices with a high resolution is a difficult problem over which people have been worried in the OLED industry. At present, although there are many different pixel designs such as the well known pixel arrangement modes of square, side by side, pentile and stripe. These pixel designs are only limited to the change in the manner in which pixels themselves are arranged, and its resolution has not yet been well improved. Meanwhile, in comparison with the film forming technology related to thin film transistors with high-precision patterning, it is difficult to put high-precision patterning into practice due to the process and equipment limitations in the evaporation and solution processes for manufacturing organic electroluminescent display devices.